Improvements in or relating to recovery of thorium from monazite

摘要

Thorium is recovered from monazite by digesting it in strong sulphuric acid at elevated temperature to form a pasty mass, cooling the paste and adding it to a large volume of water while stirring, the addition being controlled to avoid a temperature rise to above 30 DEG C., and thereafter filtering the mixture to obtain a thorium containing filtrate which is heated to about 45 DEG C., and treated with ammonia to precipitate light rare earth metal double sulphates. The resulting filtrate contains most of the thorium, which may be precipitated with oxalic acid and the oxalate obtained may then be converted into the nitrate. According to an example monazite was digested at 200 DEG C. for 4 1/2 hours in sulphuric acid of 1.84 S.g. After cooling to 20 DEG C., the grey paste was added in small quantities to a large quantity of water at 20 DEG C. while stirring and preventing the temperature rising above 30 DEG C. After standing the mixture was filtered and the filter cake washed with aqueous sulphuric acid and the combined washing and filtrate were treated at 45 DEG C. with incremental amounts of ammonia whereby light rare metal double sulphates precipitated and were separated by filtration. The precipitate was washed with warm ammonium sulphate solution and the combined filtrate and washings were then treated with oxalic acid to yield crude thorium oxalate.ALSO:Thorium is recovered from monazite by digesting it in strong sulphuric acid at elevated temperature to form a pasty mass, cooling the paste and adding it to a large volume of water while stirring, the addition being controlled to avoid a temperature rise to above 30 DEG C., and thereafter filtering the mixture to obtain a thorium containing filtrate which is heated to about 45 DEG C. and treated with ammonia to precipitate light rare earth metal double sulphates. The resulting filtrate contains most of the thorium, which may be precipitated with oxalic acid and the oxalate obtained may then be converted into the nitrate. According to an example monazite was digested at 200 DEG C. for 4 1/2 hours in sulphuric acid of 1.84 S.g. After cooling to 20 DEG C. the grey paste was added in small quantities to a large quantity of water at 20 DEG C. while stirring and preventing the temperature rising above 30 DEG C. After standing the mixture was filtered and the filter cake washed with aqueous sulphuric acid and the combined washing and filtrate were treated at 45 DEG C. with incremental amounts of ammonia whereby light rare metal double sulphates precipitated and were separated by filtration. The precipitate was washed with warm ammonium sulphate solution and the combined filtrate and washings were then treated with oxalic acid to yield crude thorium oxalate.